I think that many of the reasons given for the WHY we have short hair, don't really address the historical reasons for short hair in the military (not that I have a ready answer, but I thought I'd throw out the question).
After watching Cold Mountain and The Last Samurai on TV not too long ago (gotta love the HD PVR!!!! Record it and watch it whenever you want! But that's another issue......) I was thinking about why, in that era, soldiers had long hair, and during the later conflicts, short hair became the norm. I suspect (and could be wrong) that short hair came to being as a result of the lessons learned from that century, in regards to cleanliness and infection (ie they learned that soldiers with wounds left outside of barns, basically to die, outlived soldiers that were in better shape that were in the barns to recover, due to the unsanitary conditions.......).
Anyway, I have witnessed some different militaries of late with regard to their attitudes towards hair. I remember everybody saying how the Dutch army was full of long haired hippies, and then I worked with them in Bosnia in '00. The majority of them had shorter hair than me, and I used to be a #1 on sides and back type of guy. I asked a few guys about it, and they said it was personal preference, and that they sign something like an agreement not to embarras the Royal Dutch Army while deployed overseas with ridiculous hair (again, I could be wrong, but that was my take on how it was explained.....).
The military always has, and always will have, people who like to look "different", be it with highlights in their hair, long sideburns, handle-bar mustaches, obsolete or foreign kit (even if it is technically inferior to issue kit), tattoos, etc. I myself have recently grown a mustache (being on parental leave, I am able to avoid the jabs of my peers commenting on the cheesiness of it as it grows in.... I'm fair skinned and blonde, so it is admittedly pretty lame, but what the hell.....) and I shaved my head bald, right down to the wood, as I was in need of a haircut, and my hairline was starting the slowl march north....., and I have had tattoos since I joined. I guess nobody wants to look like everybody else, but I think it has as of late gotten a little ridiculous, particularly with some of the haircolours that people are starting to show up to work with, and some of the piercings.
A lot of the reasons can be societal or cultural as well, which I'm sure have been discussed (BTW, I didn't slog through 14 pages of posts, so I'm probably treading ground already covered, so stop reading if it's repetitive.....) already. My wife is in the military, and we have had "discussions" on why is it we want an "equal" military with regards to rights, pay, etc, but how is it that women don't have to get their heads shaved when they join, as men do??? Her reasoning (which is lame, IMHO) is that it is the norm in society for women to have long hair, and if women had to shave their heads (even once, as the great equalizer that it is meant to be in recruit training) they wouldn't join. Fair enough, but I know a lot of guys that had long (and I mean LONG) hair when they joined, and went through with it. Or how about all the potential super-soldiers out there with long hair (but NO mullets, please!!!!!) that won't join due to the current regs. Does anybody remember how hot Demi Moore looked in GI Jane???!?!?! Yes she had very little hair, if you looked north of her chest....... And I've seen more that a few women, in and out of the military, with short hair, and there was little chance of mistaking them for men.
Obviously, I am inclined to think that short hair is what should be the norm in the military for any number of reasons (hygiene, safety, appearance) but I suspect the policy makers will continue to change the regs for their reasons (increase recruiting, placate activists, etc) rather than the traditional ones.
Anyway. that's my thought on this matter.
Al